I am planning to extend my patio cover on my house. Part of the extension is going to require installing a ledger board, 2x8, along one wall on the gable end of the house. I can cut the stucco without a big problem.

What I am not exactly sure of is the water proofing afterward. Do I just use a piece of bent flashing? Stuff it under the tar paper? Do I need to cut the stucco bigger than the 2x8 so that the flashing can have a downward angle to it? Is there anyway to fit in water proof membrane? What about the ends of the flashing, and the end of the 2x8, how does that get sealed up?

I don't have a specific answer for you but I suggest looking at the online archives of Journal of Light Construction (jliconline.com) and Fine Homebuilding. I'd wager this topic has been addressed in one or both places at least once in past 25 yrs.

I have never worked with stucco, so I checked my textbooks from my construction management courses in college. They show tons of detail about how to put the mesh and beads on and apply the stucco. None of them show how to do flashing. I guess people in stucco houses aren't supposed to do additions